Authenticatable paper



United States Patent 3,523,866 AUTHENTICATABLE PAPER Wilbur W. Krueger, 500 Strollers Lane, Wausau, Wis.

54401, and John F. Dever, 1621 S. Douglas St., Appleton, Wis. 54911 No Drawing. Filed Nov. 19, 1968, Ser. No. 777,180 Int. Cl. DZlf 11/00; D21h 5/10 U.S. Cl. 162-140 5 Claims ABSTRACT OF THE DISCLOSURE Authenticatable paper containing an azoic coupling component which, upon treatment with a solution of an azoic diazo component, produces an insoluble azo dye as an identification color suitable for authenticating the paper.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to authenticatable or identifiable paper containing one component of an azo dye which is capable of producing a predetermined, distinctive, insoluble color upon treatment with the second component of an azo dye at the desired authenticating time.

Prior art It is frequently desirable to have paper, such as used for legal documents, bank notes, checks and other security documents, which can be readily identified or authenticated by the user to enable him to ascertain its genuineness. Various identifiable or authenticatable papers can be found in prior art patents. For example, US. Pat. No. 1,938,543 teaches that detecting fibers which have been specially treated with a chemically-sensitive substance can be incorporated in paper and, upon contacting such paper with an appropriate chemical agent, the detecting fibers change color and become distinguishable from the paper. As illustrated in US. Pat. No. 2,208,653, identifiable paper can also be made by including fibers of an organic ester of cellulose that have been treated with a tertiary amine. The treated fibers are visible in the paper and become fluorescent under ultraviolet light. U.S.

- Pat. No. 2,379,443 discloses identifiable paper made by the addition of a small percentage of cellulosic fibers that have been treated with hydrated ferric chloride which has been hydrolyzed to iron hydroxide. The treated fibers are capable of acquiring a deep blue color upon application to the paper of a potassium ferrocyanide solution, followed by an orthophosphoric acid solution. The prior art identifiable papers generally, however, have not proven entirely satisfactory because, for example, of their complexity of manufacture, or the papers before authentication often visibly differ from the usual type of paper, or the procedure for testing the identity or authenticity of the paper has been cumbersome; also, such prior art papers were capable of forming only a limited number of distinctive identifying colors, sometimes only one, so that many users had to use paper with the same authenticating color.

SUMMARY OF THE INVENTION The authenticatable or identifiable paper of this invention overcomes many of the problems of the prior art papers heretofore mentioned by providing a paper that contains an azoic coupling component. When the paper is contacted with a solution of an azoic diazo component, an insoluble azo dye is produced that yields a predetermined, distinctive azoic color enabling the user to easily identify or authenticate his paper. An exceptionally large 3,523,866! Patented Aug. 11, 1970 number of color-producing combinations of the aforesaid components are available so that individual users can choose a distinctive color most suitable for their purposes and not used by anyone else.

Some of the objects of this invention are: to provide an improved latently authenticatable paper that is capable of producing a predetermined, distinctive, insoluble azo dye whenever it is desired to authenticate the paper; to provide an authenticatable paper in which an exceptionally large number of authenticating colors can be developed, each peculiar to its user; to provide an authenticatable paper which is relatively easy to manufacture and use; and to provide an authenticatable paper having the several features specifically herein claimed, which is readily adaptable to various legal document and security document applications, particularly bank notes, drafts and checks.

Other objects and advantages will become apparent from the following description which sets forth several specific embodiments of this invention in a nonlirniting manner for purposes of illustrating suitable modes of practice of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with the present invention, latently authenticatable paper is prepared by incorporating in or applying to the paper a color-producing amount of an azoic coupling component.

The azoic coupling components suitable for use in the practice of the invention belong for the most part to the Naphthol AS class of coupling components. The structures of such compositions is set forth in the Colour Index, Society of Dyers and Colorists, Bradford, England, and the American Society of Textile Chemists and Colorists '(second edition, 1956, and supplements thereto), and they are identified by the term C.I. Azoic Coupling Component, which is usually followed by a number such as, for example, C.I. Azoic Coupling Component 20 to identify specific compounds within the class.

The C.I. Azoic Coupling Components useful herein generally have 0.1. numbers of CI. 37505 and higher, proceeding, for example, up to CI. 37625. The azoic coupling components within this series of Cl. numbers include the anilide of 3-hydroxy Z-naphthoic acid (Naph thol AS, CI. 37505) followed by other arylamides in increasingly complex chemical progression, those having higher C.I. numbers comprising more complicated derivatives based on the acetoacetic esters with other derivatives such as benzoyl-acetic acid esters, benzocarbazoles and dibenzofurans.

Unless specially prepared by the manufacturer, a Cl. Azoic Coupling Component is insoluble in water and is suitably converted to the water soluble salt by dissolving the Coupling Component in an alkaline solution, e.g., caustic soda, prior to being applied to paper in accordance with this invention.

The paper to be treated with the aforementioned alkaline solution of a Cl. Azoic Coupling Component can be made on any suitable papermaking machine, including Fourdrinier and cylinder machines; the papers in the following examples were made on a Fourdrinier machine. The alkaline solution of the Azoic Coupling Component can be added to the paper at any one of a number of stages in the papermaking process. The alkaline solution can be added to an aqueous slurry containing the pulp before it is fed to the papermaking machine, such as to the pulp as it is prepared, otherwise known as beater addition, or to the stock slurry; when added to the pulp slurry, the azoic coupling component becomes impregnated throughout paper made from the slurry. Also, the azoic coupling component can be added at the dry end of the papermaking machine by application at the size press, in which case the coupling component is contained both on the surface of the finished paper and partly impregnated within it. Further, the azoic coupling component can be applied to the paper by printing, in which event it is contained on the surface of the finished paper. Thus, the azoic coupling component can be contained in the paper of this invention in various forms, i.e., fully impregnating the paper with the wet end or slurry addition, partial impregnation combined with surface application with the size press addition, or being on the surface of the paper when applied by printing.

When it is desired to produce an authenticating or identifying azoic color with the paper containing a Cl. Azoic Coupling Component according to this invention, the paper is treated with a solution of a diazotised primary amine to form an insoluble azo dye. In the Colour Index, supra, the primary amines that comprise azoic diazo components are identified and referred to by a C. I. number, e.g., CI. 37005, as well as by the term C.I. Azoic Diazo Component which is usually followed by a number such as, for example, C. I. Azoic Diazo Component 2. The Diazo Components commence with C. I. 37000 and proceed, for example, to C. I. 37275. Such numbering begins with the derivatives of aniline, followed by derivatives of toluidine, anisidine, etc., and building up to the more complicated structures for compounds having higher numbers.

Azoic diazo components are usually marketed in two principal forms: (1) as the free base, hydrochloride or sulphate of a primary amine which needs to be diazotised before used in the manner well known to those skilled in the art for such chemical compounds; and (2) as stabilized diazo compounds generally referred to as Salts or Fast Color Salts. However, the latter terms must not be confused with the technical salts, hydrochlorides or sulphates of the free base. These Salts need only dissolving in cold water to be ready for use, thus eliminating the process of diazotisation, and are presently preferred for use in this invention because of their convenience of use by the person authenticating the paper.

For authentication of paper containing a C. I. Azoic Coupling Component, an aqueous solution of a Fast Color Salt or other form of the azoic diazo component is prepared and applied to the treated paper by any suitable applicator. The Fast Color Salt solutions should be used within twenty-four hours after preparing since they will become unstable and ineffective with the passage of time. An insoluble azo dye will then form in situ on such contacted portion of the paper providing a predetermined, distinctive azoic coloring, that enables the authenticity of the paper to be established. Many authenticating colors can be produced by varying the azoic coupling component in the paper and/ or varying the azoic diazo component used as the autheticating solution, so that an individual user can be assigned a particular combination to identify his specific paper.

The following examples are presented to further illustrate the paper of this invention.

EXAMPLE 1 An authenticatable paper was produced on a Fourdrinier paper machine from a furnish comprising 55 percent by weight hardwood sulfite, 35 percent by weight refined kraft and percent by weight broke to which the following were added: clay at a concentration level of 182 pounds per ton of pulp and the water soluble sodium salt of C. I. Azoic Coupling Component 29 (C. I. 37527; Naphthol ASMX) in the form of a caustic solution at a concentration level of 4 pounds of the salt per ton of pulp.

The paper web was formed at pH 7 and, after being partially dried, was fed through a size press at which a size solution containing 10 percent by weight starch, 5 percent by weight of an alkaline surface size, and 4 percent by weight of a hydrochloride chlorine indicator was applied. The latter reacts in the usual manner with chlorine ink eradicators to produce a brown color.

Upon completion of the drying, an autheticating test was performed on a specimen of the finished paper. A 1.2 percent by weight aqueous solution of C. I. Azoic Diazo Component 28 (C. I. 37151; Fast Color Salt Red PDC) was prepared by dissolving the compound in water. The solution was applied to the surface of the paper specimen to produce a permanent or insoluble plum azoic authenticating color.

EXAMPLE 2 (a) A specimen paper was produced on a Fourdrinier paper machine from a furnish comprising 60 percent by weight hardwood sulfite and 40 percent by weight refined kraft to which the following were added: alum at a concentration level of 45 pounds per ton of pulp; hydrated concentration level of 30 pounds per ton of pulp; hydrated aluminum oxide at a concentration level of 200 pounds per ton of pulp; and titanium dioxide at a concentration level of 211 pounds per ton of pulp.

After being partially dried, the paper web was fed through a size press at which a size solution containing parts by weight of starch and 0.9 part of the water souble sodium salt of a Cl. Azoic Coupling Component 2 (C. I. 37505; Naphthol AS) in the form of a caustic solution was applied. The pH of the size solution was 9.7.

Upon completion of the drying, the finished paper product was found to contain the aforesaid sodium salt at a concentration level of 0.85 pound per ton of paper. The finished paper had a basis weight of 61.2 pounds, an opacity of 92.5 percent, and a GE. brightness of 87.3 percent.

An authenticating test was performed on a specimen of the finished paper. An aqueous solution of C. I. Azoic Diazo Component 28 (C. I. 37151; Fast Color Salt Red PDC) was prepared by dissolving the compound in water. The solution was applied to the surface of the paper specimen to produce a permanent or insoluble pink azoic color.

(b) For the sake of comparison, a finished paper was prepared from the same furnish and under the same conditions as in (a) except that no azoic coupling component was added to the size solution. This paper specimen was found to have an opacity of 93 percent and a GE. brightness of 89 percent. The papers of (a) and (b) presented the same visual appearance and the casual observer would not know that paper (a) was an authenticatable paper.

For the following Examples 3-14, a slurry was made up of 100 parts by weight of pulp, comprising 60 percent hardwood sulfite, 30 percent refined kraft and 10 percent broke, to which the following were added: alum at a concentration level of 40 pounds per ton of pulp; rosin at a concentration level of 15 pounds per ton of pulp; hydrated aluminum oxide at a concentration level of pounds per ton of pulp; and titanium dioxide at a concentration level of 70 pounds per ton of pulp.

EXAMPLE 3 To a portion of the above stock slurry, there was added a caustic solution of C. I. Azoic Coupling Component 4 (C. I. 37560; Naphthol AS-BO) at a concentration level of 10 pounds of the Coupling Component per ton of slurry, the ambient pH being 4.7. The slurry was then fed to a papermaking machine, and the finished dried paper was subjected to the following authentication tests.

Authentication tests.Aqueous solutions of a number of azoic diazo components in the form of Fast Color Salts were prepared and applied to selected paper specimens. In each instance an authenticating color was produced comprising an insoluble azo dye, the resulting azoic color in each case being indicated in the following table.

TABLE I 0.I. azoic diazo com- Authenticating Fast color salt ponent No. I. No. azoic color Fast Orange Salt GGD 10 37045 Tan. Fast Scarlet Salt R 13 37130 Rust. Fast Red Salt G0 37 37035 Tan. Fast Red Salt 13.. 37125 Russet. Fast Bordeaux Salt 1 37135 Light burgundy. Fast Garnet Salt GBC. 4 37210 Burgundy. Fast Blue Salt BB 20 37175 Light blue.

EXAMPLE 4 To a portion of the above stock slurry, there was added a caustic solution of the same Coupling Component as in Example 3, the pH, however, being 7. The slurry was then fed to a papermaking machine, and the finished dried paper was subjected to authentication tests in a manner similar to Example 3, the resulting azoic color in each In a manner similar to Example 3, a caustic solution of the same Coupling Component was added to a portion of the above stock slurry except that the concentration level of such Coupling Component was 20 pounds per ton of slurry. The slurry was then fed to a papermaking machine, and the finished dried paper was subjected to authentication tests in which the resulting azoic color in each case is described below in Table III.

TABLE III 0.1. azoic diazo com- Authenticating Fast color salt ponent N 0. Cl. No. azoic color Fast Orange Salt GR 6 37025 Orangc-biege. Fast Scarlet Salt R- 13 37130 Rust. Fast Red Salt 3 GL 0 37040 Tan. Fast Bordeaux Salt G 1 37135 Burgundy. Fast Blue Salt BB 20 37175 Light blue.

EXAMPLE 6 To a portion of the above stock slurry, there was added a caustic solution of Cl. Azoic Coupling Component 3 (Cl. 37575; Naphthol AS-BR) at a concentration level of 10 pounds of the Coupling Component per ton of slurry, the ambient pH being 4.7. The slurry was then fed to a papermaking machine, and the finished dried paper was subjected to authentication tests in a manner similar to Example 3, the resulting azoic colors in each case being indicated in Table IV below.

TABLE IV 0.1. azoic diazo corn- Authenticating Fast color salt ponent No. 0.1. No. azoic color Fast Orange Salt G GD 10 37045 Cream. Fast Scarlet Salt R 13 37130 Light brown. Fast Red Salt GL 8 37110 Brown. Fast Red Salt B-.. 5 37125 Rust. Fast Red Salt PDC 28 37151 Pink. Fast Garnet Salt G0 27 37215 Brown.

EXAMPLE 7 A caustic solution of the same Coupling Component as in Example 6 was added to a portion of the above stock slurry, the pH, however, being 7. The slurry was then fed to a papermaking machine, and the finished dried paper was subjected to authentication tests in a manner similar to Example 3, the resulting azoic colors in each case being indicated in Table V below.

TABLE V 0.I. azoic diazo eom- Autheutieatlng Fast color salt ponent No. 0.1. N o. azoic color Fast Orange Salt RD 49 37050 Buff. Fast Scarlet Salt G 12 37105 Red-tan. Fast Red Salt 3 GL 9 37040 Light tan. Fast Red Salt KL 121 Pink. Fast Garnet Salt GBO 4 37210 Bronze.

EXAMPLE 8 A caustic solution of the same Coupling Component as in Example 6 was added to a portion of the above stock slurry except that the concentration level of such Coupling Component was 20 pounds per ton of slurry. The slurry was then fed to a papermaking machine, and the finished dried paper was subjected to authentication tests in a manner similar to Example 3, the resulting azoic colors in each case being indicated in Table VI below.

TABLE VI C.I. azoic diazo com- Authentlcating Fast color salt ponent No. OJ. No. azoic color Fast Scarlet Salt GG 3 37010 Light tan. Fast Red Salt AL 36 27275 ButI. Fast Red Salt PDO 28 37151 Burgundy.

EXAMPLE 9 To a portion of the above stock slurry, there was added a caustic solution of Cl. Azoic Coupling Component 20 (CI. 37530; Naphthol AS-OL) at a concentration level of 10 pounds of the Coupling Component per ton of slurry, the ambient pH being 4.7. The slurry was then fed to a papermaking machine, and the finished dried paper was subjected to authentication tests in a manner similar to Example 3, the resulting azoic colors in each case being indicated in Table VII below.

TABLE VII 0.1. azoic diazo com Authenticating Fast colorsalt ponent No. 0.1. No. azoic color Fast Orange Salt GGD 16 37045 Cream. Fast Scarlet Salt R 13 37130 Rust. Fast Red Salt GL 8 37110 Burgundy. Fast Red Salt RC-.. 10 37120 Tan. Fast Red Salt KL 121 Rose. Fast Bordeaux Salt GP 1 37135 Light burgundy.

EXAMPLE 10 A caustic solution of the same Coupling Component as in Example 9 was added to a portion of the above stock slurry, the pH, however, being 7. The slurry was then fed to a paper making machine, and the finished dried paper was subjected to authentication tests in a manner similar to Example 3, the resulting azoic colors in each case being indicated in Table VIII below.

TABLE VIII 0.1. azoic diazo eom- Authenticatlng Fast color salt ponent No. 01. No. azoic color Fast Orange Salt RD 49 37050 Light orange. Fast Scarlet Salt G 12 37105 Rose. Fast Red Salt 3 GL. 9 37040 Red-brown. Fast Red Salt B.-." 5 37125 Russet. Fast Red Salt FR 33 37075 Tan. Fast Garnet Salt GBO 4 37210 Burgundy.

EXAMPLE 11 A caustic solution of the same Coupling Component as in Example 9 was added to a portion of the above stock slurry except that the concentration level of such Coupling Component was 20 pounds per ton of slurry. The slurry was then fed to a paperrnaking machine, and the finished dried paper was subjected to authentication tests in a manner similar to Example 3, the resulting azoic colors in each case being indicated in Table IX below.

TABLE IX C.I. azoic diazo com Authenticating Fast color salt ponent No. 0.1. No. azoic color Fast Scarlet Salt GG 3 37010 Light tan.

37275 Red-brown. 37151 ink.

P 37175 Light purple.

Fast Blue Salt BB EXAMPLE 12 TABLE X 0.1. azoic diazo com Authentlcating Fast color salt ponent No. 0.1. No. azoic color Fast Orange Salt GGD 16 37045 Orange. Fast Red Salt GG 37 37035 Light gold. Fast Red Salt BL... 34 37100 Gold. Fast Red Salt TR 11 37085 Pink. Fast Bordeaux Salt GP 1 37135 Light purple. 90 Fast Violet Salt B 41 27165 Light violet.

EXAMPLE 13 A caustic solution of the same Coupling Component as in Example 12 was added to a portion of the above stock slurry, the pH, however, being 7. The slurry was then fed to a papermaking machine, and the finished dried paper was subjected to authentication tests in a manner similar to Example 3, the resulting azoic colors in each case being indicated in Table XI below.

TABLE XI 0.1. azoic diazo com Authenticating Fast color salt ponent No. 01. No. azoic color Fast Orange Salt RD 49 37050 Red-orange. Fast Red Salt GL 8 37110 Light pruple.

Fast Red Salt AL 36 37275 Light tan.

Fast Garnet Salt GBC 4 37210 Dark purple.

EXAMPLE 14 A caustic solution of the same Coupling Component as r in Example 12 was added to a portion of the above stock slurry except that the concentration level of such Coupling Component was 20 pounds per ton of slurry. The slurry was then fed to a papermaking machine, and the finished dried paper was subjected to authentication tests in a 50 manner similar to Example 3, the resulting azoic colors in each case being indicated in Table XII below.

TABLE XII C.I. azoic (5O diazo com Authenticatlng Fast color salt ponent No. 0.1. No. azoic color Fast Scarlet Salt R 13 37130 Rust. Fast Red Salt 3 GL 9 3704.0 Tan. Fast Red Salt B 6 37125 Russet. Fast Blue Salt BB 20 37175 Light purple.

EXAMPLE 15 An oflYset press printing process was used to apply the azoic coupling component to the finished paper. Instead of the usual ink-containing offset press fountain solution, there was added to the fountain the sodium salt of Cl. Azoic Coupling Component 2 (CI. 37505; Naphthol AS) in the form of a caustic solution at a concentration level of 0.8 pound of the salt per gallon of solution. A blank plate was mounted on the plate cylinder, and rubber plates were mounted on the blanket cylinder in the usual manner. The fountain solution was transferred by dampeners to the blank plate, and from there to the rubber plates. A sheet of finished white printing paper was fed to the press, and the pressure of the rubber plates against the paper transferred the solution to the paper surface in the form of a rectangularly shaped design which was invisible to the casual observer.

An authenticating test was performed on a specimen of the printed paper. An aqueous solution of Cl. Azoic Diazo Component 41 (CI. 37165; Fast Color Salt Violet B) was prepared by dissolving the compound in water. The solution was applied to the surface of the specimen to produce an authenticating visible design having an insoluble plum azoic color.

Similar results were obtained using a letterset printing process and a flexographic printing process. Conventional flexographic type equipment is used in which the Azoic Coupling Component solution is metered to the rubber plate cylinder. The paper web passes between the printing cylinder and a backing roll, and the pressure of the backing roll forces the paper against the plate cylinder to transfer the solution to the paper. The web is rewound or sheeted as desired after being printed with the Azoic Coupling Component solution. With the letterset process, the Azoic Coupling Component solution is applied to the plate [dycril] with a dampening system. The dycril plate then transfers the solution to the conventional blanket and the blanket transfers the solution to the paper. This is a sheet fed operation. Because of the low viscosity of this solution, the dampening system should be used.

EXAMPLE 16 A specimen paper was produced on a Fourdrinier paper machine from a furnish comprising 55 percent by weight hardwood sulfite, 35 percent by weight refined kraft, and 10 percent by weight broke to which the following were added: alum at a concentration level of 35 pounds per ton of pulp; rosin at a concentration level of 9 pounds per ton of pulp; clay at a concentration level of pounds per ton of pulp; titanium dioxide at a concentration level of 50 pounds per ton of pulp; hydrated aluminum oxide at a concentration level of 50 pounds per ton of pulp; and the water soluble sodium salt of Cl. Azoic Coupling Component 2 (CI. 37505; Naphthol AS) in the form of a caustic solution at a concentration level of 10 pounds of the salt per ton of pulp.

Part of the Coupling Component in the paper was reacted with a 1.2 percent by weight aqueous solution of Cl. Azoic Diazo Component 6 (Cl. 37025; Fast Color Salt Orange GR) to produce a permanent pattern of an insoluble light orange-beige azoic color in the paper, while still leaving a sufficient quantity of unreacted Coupling Component to provide an authenticatable paper.

An authenticating test was performed on a specimen of the finished, patterned paper by applying an aqueous solution of the same Azoic Diazo Component 6 to yield an insoluble light orange-beige authenticating azoic color in the paper causing the pattern to disappear where the paper was authenticated. A second authenticating test was performed on another specimen of the finished, patterned paper by applying an aqueous solution of Cl. Azoic Diazo Component 20 (Cl. 37175; Fast Color Salt Blue BB) to yield an insoluble blue authenticating azoic color in the paper appearing around the orange'beige pattern.

The C1. Azoic Coupling Components used in the practice of this invention are particularly advantageous because they are relatively easy to incorporate in or apply to the paper and demonstrate a strong affinity for the paper fibers. The latently authenticatable paper should contain a sufiicient quantity of the Coupling Component to produce the color shade desired for authentication, which will vary with the quantity of Coupling Component contained in the paper. An Azoic Coupling Component concentration in the range of about 0.25 pound (of unreacted Coupling Component) per ton of paper, and above, is capable of producing an authenticatable color change upon contact with a Diazo Component. The concentration of the Diazo Component solution used for authentication will also affect the shade or intensity of the color that is produced; solutions on the order of 0.5% by weight, and above, are satisfactory for obtaining an authentication color, with a 1.2% by weight solution generally being capable of reacting with all of the Coupling Component added to the paper at the levels used in the preceding examples. Because the Coupling Component can be put in or on the paper Without significantly changing either the base color of the paper or its visual appearance, the latently authenticatable paper of this invention can have the customary appearance of the usual white paper; however, as shown in Example 16, the paper can also be partially or completely colored with an azoic color, but have unreacted Coupling Component available for authentication. Also, once the Coupling Component has been applied to the paper, the paper can then be printed upon and the azoic color produced in the manner herein described will still appear around the printed matter.

Another advantage of the Coupling Components used herein is that with a single Coupling Component a multiplicity of predetermined azoic color combinations can be provided merely by contacting such component with a different particular C.I. Azoic Diazo Component. The range of authenticating colors can be further extended by using mixtures of the Coupling Components in the paper, and/or mixtures of the Azoic Diazo Components for the authenticating solutions. The wide variety of specific color reactions provided with the authentication papers of this invention has the extremely valuable advantage of enabling a particular color reaction to be reserved for a specific user so that only he will know the authentication color that is to be produced; this also enables ditferent authenticating colors to be used at different times should a time-coded authentication feature be desirable. As has been stated in the preceding description, the authenticating azoic color becomes permanent, or insoluble, after the Azoic Diazo Component solution has been added to the paper containing a Coupling Component, and this presents the advantage that the authenticating color cannot be removed without destroying the paper. Thus the latently authenticatable papers of this invention are capable of providing immediate, highly visible and lasting authentication color reactions herebefore unobtainable with prior art papers in this general field.

We claim:

1. As a new article of manufacture, a latently authenticatable paper containing, as the sole component of an azoic color, an azoic coupling component, said azoic coupling component being present in an amount suflicient to produce an authenticating azoic color upon the application of an azoic diazo component to the paper.

2. The paper of claim 1 wherein the azoic coupling component is printed on the surface of the paper.

3. The paper of claim 1 wherein the azoic coupling component is at least partially impregnated within the paper.

4. An authenticatable paper according to claims 1, 2 or 3 wherein the azoic coupling component is C.I. 37505, C.I. 37525, C.I. 37527, C.I. 37530, C.I. 37560, or C.I. 37575.

5. An authenticatable paper according to claims 1, 2 or 3 wherein the azoic diazo component is C.I. 37010, C.I. 37025, C.I. 37035, C.I. 37040, C.I. 37045, C.I. 37050, C.I. 37075, C.I. 37085, C.I. 37100, C.I. 37105, C.I. 37110, C.I. 37120, C.I. 37125, C.I. 37130, C.I. 37135, C.I. 37151, C.I. 37165, C.I. 37170, C.I. 37175, C.I. 37210, C.I. 37215, or C.I. 37275.

References Cited Casey, J. P.: Pulp and Paper, 2nd ed., N.Y., Interscience, 1960, vol. II, p. 1224.

HOWARD R. CAlNE, Primary Examiner U.S. Cl. X.R. 

